U.S. patent number 6,700,662 [Application Number 09/767,104] was granted by the patent office on 2004-03-02 for portable lii based instrument and method for particulate characterization in combustion exhaust.
This patent grant is currently assigned to The University of Chicago. Invention is credited to Sreenath B. Gupta, Ramanujam Raj Sekar.
United States Patent |
6,700,662 |
Gupta , et al. |
March 2, 2004 |
**Please see images for:
( Reexamination Certificate ) ** |
Portable LII based instrument and method for particulate
characterization in combustion exhaust
Abstract
An improved instrument and method are provided for particulate
characterization in combustion exhausts. An instrument for
measuring particles of combustion exhausts includes a laser for
producing a high intensity laser pulse. A sample cell receives a
combustion exhaust input and the high intensity laser pulse. At
least one detector detects a signal generated by particles in said
received combustion exhaust input. The detected signal includes
laser induced incandescence (LII). Signal conditioning electronics
is coupled to the detector and particle data is displayed during
transient operation of a combustion engine. Data related to mass
concentration, number density, and particle size of particles in
the received combustion exhaust input is measured and
displayed.
Inventors: |
Gupta; Sreenath B. (Naperville,
IL), Sekar; Ramanujam Raj (Naperville, IL) |
Assignee: |
The University of Chicago
(Chicago, IL)
|
Family
ID: |
25078492 |
Appl.
No.: |
09/767,104 |
Filed: |
January 22, 2001 |
Current U.S.
Class: |
356/336; 356/335;
356/338 |
Current CPC
Class: |
G01N
21/718 (20130101); G01N 21/716 (20130101) |
Current International
Class: |
G01N
21/71 (20060101); G01N 015/02 (); G01N
021/00 () |
Field of
Search: |
;356/337,338,335,336,334,339,392,43,46,47,315,317,318
;250/573-575,554 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
5142140 |
August 1992 |
Yamazaki et al. |
6154277 |
November 2000 |
Snelling et al. |
6181419 |
January 2001 |
Snelling et al. |
6473178 |
October 2002 |
Shimaoka |
|
Other References
Snelling et al. "Particulate Matter Measurements in a Diesel Engine
Exhaust by Laser-Induced Incandescence and Standard Gravimetric
Procedure" Oct. 1999, SAE Technical Paper Series 1999-01-3653, SAE
International Fall Fuels and Lubricants Meeting..
|
Primary Examiner: Adams; Russell
Assistant Examiner: Sever; Andrew
Attorney, Agent or Firm: Pennington; Joan
Government Interests
CONTRACTUAL ORIGIN OF THE INVENTION
The United States Government has rights in this invention pursuant
to Contract No. W-31-109-ENG-38 between the United States
Government and Argonne National Laboratory.
Claims
What is claimed is:
1. An instrument for measuring particles of combustion exhausts
comprising: a laser for producing a high intensity laser pulse; a
sample cell for receiving combustion exhaust input and said high
intensity laser pulse; a plurality of optical elements coupling
said high intensity laser pulse to said sample cell; said plurality
of optical elements including a plurality of cylindrical lenses;
and at least one detector for detecting a signal generated by
particles in said received combustion exhaust input, said signal
including laser induced incandescence (LII).
2. An instrument for measuring particles of combustion exhausts as
recited in claim 1 further includes a plurality of focusing
elements coupling said signal generated by particles in said
received combustion exhaust input in said sample cell to said at
least one detector.
3. An instrument for measuring particles of combustion exhausts as
recited in claim 1 includes a dilution tunnel coupling said
combustion exhaust input to said sample cell.
4. An instrument for measuring particles of combustion exhausts
comprising: a laser for producing a high intensity laser pulse; a
sample cell for receiving combustion exhaust input and said high
intensity laser pulse; at least one detector for detecting a signal
generated by particles in said received combustion exhaust input,
said signal including laser induced incandescence (LII); and a
pIurality of focusing elements coupling said signal generated by
particles in said received combustion exhaust input in said sample
cell to said at least one detector; said plurality of focusing
elements including a plurality of spherical lenses.
5. An instrument for measuring particles of combustion exhausts as
recited in claim 4 further includes a plurality of optical elements
coupling said high intensity laser pulse to said sample cell.
6. An instrument for measuring particles of combustion exhausts as
recited in claim 4 further includes a filter for filtering said
signal generated by particles in said received combustion exhaust
input.
7. An instrument for measuring particles of combustion exhausts as
recited in claim 4 further includes signal conditioning electronics
coupled to said at least one detector.
8. An instrument for measuring particles of combustion exhausts as
recited in claim 7 wherein said signal conditioning electronics
includes a peak detector.
9. An instrument for measuring particles of combustion exhausts as
recited in claim 7 wherein said signal conditioning electronics
includes a calibration multiplier.
10. An instrument for measuring particles of combustion exhausts as
recited in claim 7 wherein said signal conditioning electronics
includes a display for displaying particle measurements.
11. An instrument for measuring particles of combustion exhausts as
recited in claim 4 includes a display coupled to said at least one
detector for displaying data related to mass concentration, number
density, and particle size of particles in said received combustion
exhaust input.
12. An instrument for measuring particles of combustion exhausts as
recited in claim 4 wherein said at least one detector for detecting
a signal generated by particles in said received combustion exhaust
input detects said signal during transient operation of an
engine.
13. An instrument for measuring particles of combustion exhausts as
recited in claim 4 wherein said at least one detector for detecting
a signal generated by particles in said received combustion exhaust
input includes at least one photo-multiplier tube (PMT)
detector.
14. An instrument for measuring particles of combustion exhausts as
recited in claim 4 wherein said at least one detector for detecting
a signal generated by particles in said received combustion exhaust
input includes a pair of photo-multiplier tube (PMT) detectors.
15. An instrument for measuring particles of combustion exhausts as
receted in claim 14 includes signal conditioning electronics
coupled to each of said pair of photo-multiplier tube (PMT)
detectors.
16. A method for measuring particles of combustion exhausts
comprising the steps of: utilizing a laser, producing a high
intensity laser pulse; receiving a combustion exhaust input in a
sample cell; coupling said high intensity laser pulse to said
sample cell using a plurality of optical elements; said plurality
of optical elements including a plurality of cylindrical lenses;
and detecting a signal generated by particles in said received
combustion exhaust input, said signal including laser induced
incandescence (LII).
17. A method for measuring particles of combustion exhausts as
recited in claim 16 further includes the steps of conditioning said
detected signal and displaying data related to the particles in
said received combustion exhaust input.
18. A method for measuring particles of combustion exhausts as
recited in claim 17 wherein the step of displaying data related to
the particles in said received combustion exhaust input includes
the steps of displaying data related to mass concentration, number
density, and particle size of particles in said received combustion
exhaust input.
19. A method for measuring particles of combustion exhausts as
recited in claim 16 wherein the step of detecting a signal
generated by particles in said received combustion exhaust input
includes the detecting a signal generated by particles in said
received combustion exhaust input during transient operation of an
engine.
Description
FIELD OF THE INVENTION
The present invention relates to an instrument and method for
particulate characterization in combustion exhausts, and more
particularly relates to a method and portable instrument based on
laser induced incandescence (LII) to measure particulate content
and primarily mass emissions (gms/cm.sup.3) of combustion exhausts,
such as from diesel engines.
DESCRIPTION OF THE RELATED ART
Particles emitted from diesel engines pose a significant health
hazard to the general public because these particles are of the
right size to be inhaled and deposited deep inside the lungs. An
additional concern is that certain substances that condense on the
surface of these particles are carcinogenic.
Newer particulate standards imposed by the Environmental Protection
Agency (EPA) have serious implications toward the future operation
of combustion equipment. Current research efforts to curtail
particulate emissions are limited by the lack of proper measurement
techniques. The known measurement techniques require expensive
instrumentation with equally matching demands on operator skill and
time. One widely accepted EPA approved technique entails the
collection of particulates using a filter paper in a diluted stream
of exhaust gases, which is followed by gravimetry. Alternate
measurement techniques are based upon light extinction or
reflection principles. Efforts to obtain quantitative measurements
based upon such principles have resulted in little success.
Techniques used in air sampling only are effectively used for
measuring particle number concentrations, N (particles/cm.sup.3).
However, large response-times, such as 120 seconds, preclude their
use for transient evaluations.
Laser induced incandescence (LII), a recently developed technique
facilitates real-time quantitative planar imaging of soot
emissions. A doctoral thesis by Sreenath B. Gupta at Pennsylvania
State University in December, 1996 entitled "CHEMICAL MECHANISTIC
APPROACHES TO SOOT CONTROL IN LAMINAR DIFFUSION FLAMES" describes
the use of laser induced incandescence (LII) in characterizing the
soot field in flames.
It is an object of the invention to provide an improved instrument
and method for particulate characterization in combustion
exhausts.
It is another object of the invention to provide an improved method
and instrument based on laser induced incandescence (LII) to
measure particulate content and primarily mass emissions
(gms/cm.sup.3) of combustion exhausts.
It is another object of the invention to provide an improved method
and instrument based on laser induced incandescence (LII) to
measure particulate content and primarily mass emissions
(gms/cm.sup.3) of combustion exhausts during transient operation of
an engine.
It is another object of the invention to provide such improved
method and instrument for measuring particle size in nanometers and
number density or number of particles per cubic centimeter and mass
concentration or grams of particles per cubic centimeter
(gms/cm.sup.3) of combustion exhausts during transient operation of
an engine.
It is another object of the invention to provide such instrument
that is a compact and portable device and that enables fast, easy,
and cost-effective characterizing of particles of combustion
exhausts.
It is another object of the invention to provide such improved
method and instrument substantially without negative effect and
that overcome many of the disadvantages of prior arrangements.
SUMMARY OF THE INVENTION
In brief, an improved instrument and method are provided for
particulate characterization in combustion exhausts. An instrument
for measuring particles of combustion exhausts includes a laser for
producing a high intensity laser pulse. A sample cell receives a
combustion exhaust input and the high intensity laser pulse. At
least one detector detects a signal generated by particles in said
received combustion exhaust input. The detected signal includes
laser induced incandescence (LII).
In accordance with features of the invention, signal conditioning
electronics is coupled to the detector and particle data is
displayed during transient operation of a combustion engine. Data
related to mass concentration, number density, and particle size of
particles in the received combustion exhaust input is measured and
displayed.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention together with the above and other objects and
advantages may best be understood from the following detailed
description of the preferred embodiments of the invention
illustrated in the drawings, wherein:
FIG. 1 is a block diagram representation of a portable instrument
based on laser induced incandescence (LII) to measure particulate
content and primarily mass emissions (gms/cm.sup.3) of combustion
exhausts, such as from diesel engines in accordance with the
preferred embodiment;
FIG. 2 is a diagrammatic top view of the portable instrument of
FIG. 1 in accordance with the preferred embodiment; and
FIG. 3 is a diagrammatic front view of the portable instrument of
FIG. 1 in accordance with the preferred embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Having reference now to the drawings, in FIG. 1 there is shown a
block diagram representation of a portable instrument in accordance
with the preferred embodiment based on laser induced incandescence
(LII) to measure particulate content and primarily mass emissions
(gms/cm.sup.3) of combustion exhausts, such as from diesel engines,
generally designated by the reference number 100. LII portable
combustion exhaust measurement instrument 100 includes a laser 102
producing a high intensity laser beam pulse. The laser beam pulse
is coupled through a plurality of optical elements 104 and applied
to a sample cell 106. The sample cell 106 receives an exhaust
input. Laser induced incandescence (LII) is used to measure
particulate content and primarily mass emissions (gms/cm.sup.3) of
the combustion exhaust applied to the sample cell 106. A beam trap
108 is coupled to the sample cell 106.
In accordance with features of the preferred embodiment, with the
laser induced incandescence (LII) technique, a high-energy laser
pulse heats the tiny particles in combustion exhausts. Upon
heating, the particles emit light, which, when collected
appropriately, indicates particulate content and primarily mass
emissions (gms/cm.sup.3) of combustion exhausts. LII portable
combustion exhaust measurement instrument 100 measures mean
particle size in nanometers, number density or number of particles
per cubic centimeter, and the mass concentration or grams per cubic
centimeter. LII portable combustion exhaust measurement instrument
100 enables characterizing particles in a fast, easy, and
cost-effective way. LII portable combustion exhaust measurement
instrument 100 is used in real time, that is during transient
operation of an engine. LII portable combustion exhaust measurement
instrument 100 is a compact and portable instrument.
LII portable combustion exhaust measurement instrument 100 includes
a plurality of detectors 110 coupled to the sample cell 106, such
as a pair of photo-multiplier tube (PMT) detectors PMT1, PMT2110.
PMT detectors 110 detect a signal generated by particles in the
combustion exhaust.
Signal conditioning electronics 112 is coupled to the detectors 110
to characterize, in real time during transient operation of an
engine, particulate emissions in the combustion exhaust, such as of
diesel engines. Signal conditioning electronics 112 includes a pair
of peak detectors 114 respectively coupled to the PMT detectors 110
and providing a peak detected signal to a respective calibration
multiplier 116. One of the calibration multipliers 116 provides a
calibrated signal to a display 120 for displaying mass
concentration (gms/cc) measured values in real time during
transient operation of an engine. The calibration multipliers 116
are coupled by an arithmetic operator block 118 to display 120 for
displaying number density (#/cc) and particle diameter (nm)
measured values in real time during transient operation of an
engine.
In the LII portable combustion exhaust measurement instrument 100,
the combustion exhaust stream is partially sampled by a vacuum
generated by a dilution tunnel 122. In this tunnel 122 the exhaust
sample stream is diluted using filtered air in a predetermined
ratio. The diluted sample stream is then passed through the sample
cell 106, to be finally exhausted out of the instrument 100. The
high intensity emission from a pulsed laser 102 is expanded as a
vertical sheet and focused onto the center of the sample cell 106
using multiple optical elements 104. The laser beam is finally
terminated using the beam trap 108. Upon the incidence of the laser
pulse, the particles in the combustion exhaust within sample cell
106 are heated to their sublimation temperature and emit thermal
radiation as they cool down. This laser induced incandescence (LII)
emission when appropriately collected by detectors 110 is directly
proportional to the local mass concentration (gms/cc). This signal
is focused using a train of optical elements including a first
spherical lens S1, a second spherical lens S2 and an aperture with
a blue interference filter F1 as shown in FIG. 2, onto a PMT1
detector 110. Similarly, the Rayleigh scattering signal is focused
onto a second PMT2 detector 110. This signal is focused onto PMT2
detector 110 using a second set of optical elements including a
first spherical lens S3, a second spherical lens S4 and an aperture
with a green filter F2.
Signal conditioning electronics 112 is coupled to the PMT1, PMT2
detectors 110 reflect the following relations:
Respective signals from each PMT detectors PMT1, PMT2110 are passed
to a set of signal processing electronics 112. The peaks of the
signals are detected by the peak detection circuitry 114, and then
are further multiplied by calibration factors by the calibration
multiplier circuitry 116. The resulting signals are further
processed by an arithmetic operator 118 to obtain mean particle
diameter (nm) and number density (number of particles/cm3).
However, the processed signal from PMT1110 directly results in mass
concentration (gms/cc) and is routed to the numeric display
120.
In accordance with features of the preferred embodiment, LII
portable combustion exhaust measurement instrument 100 provides
data on the three parameters that are essential for understanding
diesel exhausts; the mass concentration, number density, and mean
size of the particles. LII portable combustion exhaust measurement
instrument 100 by providing effective real time measurements can
enable development of technologies to reduce particulate emissions.
Certain transient phases of engine operation result in increased
emission of particles, for example, an engine accelerating from
idle. Because conventional instruments cannot measure particles
during transient operation, engine designers are unable to
fine-tune the engine parameters to reduce the emission of particles
during transient operation. LII portable combustion exhaust
measurement instrument 100 with its ability to collect information
during transient operations can assist engine designers to design a
cleaner-burning engine.
Referring also to FIGS. 2 and 3, more details of optical elements
104 and signal focusing and filtering of the signal generated by
the particles of the LII portable combustion exhaust measurement
instrument 100 are shown. LII portable combustion exhaust
measurement instrument 100 has a two layer construction. A top
layer includes the laser 102, optical elements 104, the sample cell
106, detectors 110 and the signal conditioning electronics 112. A
lower layer includes a dilution tunnel 122 shown in dotted line to
dilute the exhaust sample using air. LII portable combustion
exhaust measurement instrument 100 includes a housing 124 that
contains the two layer construction. The display 120 is carried by
the housing 124 for viewing measured results by the user.
As shown in FIG. 2, optical elements 104 includes a pair of
elements E1, E1 for turning the laser beam through 90 degrees twice
to pass through a plurality of cylindrical lenses C1, C2 and C3.
The resulting laser beam passes through the sample cell 106. The
beam trap 108 captures the laser beam from the sample cell 106. The
signal generated by the particles is focused by two spherical
lenses S1 and S2 onto the aperture/blue filter F1. This focused
signal is filtered by a blue interference filter F1 before being
detected by the PMTI detector 110. The Rayleigh scattering signal
is similarly focused onto PMT2 detector 110 by two spherical lenses
S3 and S4 onto the aperture/green filter F2.
While the present invention has been described with reference to
the details of the embodiments of the invention shown in the
drawing, these details are not intended to limit the scope of the
invention as claimed in the appended claims.
* * * * *